cost

Estimate cost of implementing filter System object

Syntax

c = cost(sysobj)

c = cost(sysobj,Arithmetic=arithType)

Description

c = cost(sysobj) returns a structure, c, whose fields contain information about the computational cost of implementing the filter System object™, sysobj.

c = cost(sysobj,Arithmetic=arithType) returns a cost estimate c for the filter System object sysobj in the arithmetic specified by arithType.

Examples

Cost of FIR Filter

This example shows how to compute the cost of implementing an FIR Filter created using dsp.FIRFilter object.

Fs = 8000; 
Fcutoff = 2000;
firFilt = dsp.FIRFilter('Numerator',designLowpassFIR(FilterOrder=130,CutoffFrequency=Fcutoff/(Fs/2)));
cost(firFilt)

ans = struct with fields:
                  NumCoefficients: 131
                        NumStates: 130
    MultiplicationsPerInputSample: 131
          AdditionsPerInputSample: 130

Input Arguments

sysobj — Input filter

filter System object

Input filter, specified as one of the following filter System objects:

• dsp.AllpassFilter

• dsp.AllpoleFilter

• dsp.CICCompensationDecimator

• dsp.CICCompensationInterpolator

• dsp.CICDecimator

• dsp.CICInterpolator

• dsp.CoupledAllpassFilter

• dsp.Delay

• dsp.Differentiator

• dsp.FarrowRateConverter

• dsp.FilterCascade

• dsp.FIRDecimator

• dsp.FIRFilter

• dsp.FIRHalfbandDecimator

• dsp.FIRHalfbandInterpolator

• dsp.FIRInterpolator

• dsp.FIRRateConverter

• dsp.FourthOrderSectionFilter

• dsp.HighpassFilter

• dsp.IIRFilter

• dsp.IIRHalfbandDecimator

• dsp.IIRHalfbandInterpolator

• dsp.LowpassFilter

• dsp.NotchPeakFilter

• dsp.ParallelFilter

• dsp.SOSFilter

• dsp.VariableBandwidthFIRFilter

• dsp.VariableBandwidthIIRFilter

• dsp.VariableFIRDecimator

• dsp.VariableFIRInterpolator

arithType — Arithmetic type

'double' (default) | 'single' | 'Fixed'

Arithmetic used in the filter analysis, specified as 'double', 'single', or 'Fixed'. When the arithmetic input is not specified and the filter System object is unlocked, the analysis tool assumes a double-precision filter. When the arithmetic input is not specified and the System object is locked, the function performs the analysis based on the data type of the locked input.

The 'Fixed' value applies to filter System objects with fixed-point properties only.

When the 'Arithmetic' input argument is specified as 'Fixed' and the filter object has the data type of the coefficients set to 'Same word length as input', the arithmetic analysis depends on whether the System object is unlocked or locked.

• unlocked –– The analysis object function cannot determine the coefficients data type. The function assumes that the coefficients data type is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.

• locked –– When the input data type is 'double' or 'single', the analysis object function cannot determine the coefficients data type. The function assumes that the data type of the coefficients is signed, has a 16-bit word length, and is auto scaled. The function performs fixed-point analysis based on this assumption.

To check if the System object is locked or unlocked, use the isLocked function.

When the arithmetic input is specified as 'Fixed' and the filter object has the data type of the coefficients set to a custom numeric type, the object function performs fixed-point analysis based on the custom numeric data type.

Output Arguments

c — cost estimate

struct

Cost estimate, c contains the following fields:

Estimated Value	Description
NumCoefficients	Number of filter coefficients (excluding coefficients with values 0, 1 or -1)
NumStates	Number of filter states
MultiplicationsPerInputSample	Number of multiplication operations performed for each input sample
AdditionsPerInputSample	Number of addition operations performed for each input sample

Version History

Introduced in R2011a

R2024b: Support for dsp.VariableFIRDecimator and dsp.VariableFIRInterpolator Objects

Starting in R2024b, the cost analysis function supports the dsp.VariableFIRDecimator and dsp.VariableFIRInterpolator objects.

R2024b: dsp.BiquadFilter object warns

The dsp.BiquadFilter object issues a warning and will be removed in a future release. Use the dsp.SOSFilter object instead. For more information on how to replace your existing code, see the Compatibility Considerations section in the dsp.BiquadFilter reference page.

R2023b: Support for dsp.ParallelFilter and dsp.Delay Objects

Starting in R2023b, the cost analysis function supports the dsp.ParallelFilter and the dsp.Delay objects.

R2023b: dsp.BiquadFilter object will be removed

The dsp.BiquadFilter object will be removed in a future release. Use the dsp.SOSFilter object instead.